Here are some things I have done. I already found the volume since the other part of the question said to use the method of discs/washers. It is 54.0633 cubic units (correct answer).

I found by trial and error that (since this is an online assignment) that a= 9/sqrt(82) and c =9 .

What do I do? Why should there be two integrals, I don't understand.

I have tried the following.

y = 9^x becomes x = lny/ln9

Formula

h = lny/ln9

r = y

So I got integral from 9/sqrt(82) to 9 of

dy

But that's just one integral and perhaps even incorrect. Please show me what to do.

Thanks